In almost all lighting applications, the distribution of light from the source is fixed in time. Lights can be turned on and off and/or dimmed but the distribution of the photons that do leave the source is generally static. This means that much of the light is not going into a useful direction. There are two limits to this problem. In an incandescent bulb, the light is emitted almost uniformly in space, essentially equally intense in all directions. Typical light fixtures try to compensate for this by having mirrors or other reflecting surfaces inside the luminaire to direct the light to where it is wanted. Laser diodes are in the opposite limit. While extremely efficient in terms of generating photons from electrons, they emit light that is uni-directional, a tightly collimated beam. For luminaires built with these sources, one has the opposite problem, that of diffusing a collimated beam. This is typically done with some kind of translucent element such as a plastic dome. But in either solution the distributions do not change in time.